There are several ways, depending on your situation. In all cases, it depends on having or adding a negative index in the block command.
1. Put shells around the block. If you start out with
block 1 11; 1 11; 1 11; -1 1 -1 1 -1 1;
then change to the following:
block -1 0 2 12 0 -13;-1 0 2 12 0 -13; -1 0 2 12 0 -13;
-1 0 -1 1 0 1 -1 0 -1 1 0 1 -1 0 -1 1 0 1
Be sure to do the same thing to the shells that are done to the solids. Alternatively, use the bb command to glue the shell to the block and the shell will follow the shape of the solid.
2. Add shells to the part. Use the insprt command and add a new shell partition before the first partition (left side) or after the last partition (right side).
3. Add a new part with just shells. Copy the commands that formed the first part and modify the block command by adding the minus sign on the indices that correspond to the shells. You may need to delete unwanted solids or undo commands that only have meaning for solids.
